Which of the following statements is incorrect ? (1) Oxidation-reduction reactions produce proton gradient in respiration. (2) During aerobic respiration, role of oxygen is limited to the terminal stage. (3) In ETC (Electron Transport Chain), one molecule of NADH+H+ gives rise to 2 ATP molecules, and one FADH2 gives rise to 3 ATP molecules. (4) ATP is synthesized through complex V.